Nematodes Flashcards
___ is a hallmark of parasitic infection
Eosinophilia
Generally, how do Helmminths cause damage to the host?
Mechanical damage and attachment
Nutritional depletion
Immunopathology
Ways that helminths conduct mechanical attachment and damage (4)
Internal organ blockade (Ascaris and filaria)
Pressure atrophy (Ascaris)
Mechanical damage (hookworm and whipworm)
Tissue migration (helminth larvae)
What are 3 examples of nutrient depletion by helminths?
Iron deficiency (hookworm and whipworm - burrow and get blood from the blood stream)
Vitamin A sequestration - (Ascaris) - sequesters vitamin A and uses it for reproduction)
Macronutrients (Stronglyloides, Ascaris)
3 examples of immunopathology caused by helminths are__
Anaphylaxis
Immune complex deposition
Modulated cell-mediated immune response
**note that filaria does all of the above**
Describe the lifecycle of nematodes
Eggs >> 4 larval stages >> adults
Some become males and females. Males fertilize females, females release embryonated eggs that then grow to become L1s. L1s shed their outside cuticle (aka molting) and become L2’s >> L3>> L4 >> adults
Which stage in the nematode life cycle is the infective stage?
The infective stage is the L3
Some of the soil transmitted parasites are released into the environment via feces
Depending on the bug, the embryonated eggs can lie dormant until they’re picked up by the human host and hatch as an L1 larvae and continue the cycle inside the human host
Sometimes the bugs are taken up by insects and complete their life cycle inside insects
Other times, the larvae progress all the way through L4 out in the environment (e.g. hookworm) before we pick them up
Describe the life cycle of a pin worm (hint: the vermin lady crawling out of the anus)
Enterobius vermicularis – the vermin lady (lays eggs in anus, causes anal itching)
Lifecycle of pinworm: eggs on hands >> hands in mouth >> eggs swallowed >> eggs travel thru intestine and hatch >> males and females reproduce/females lay more eggs in per-anal area >> anal itching = auto-infection or spreading eggs by touching other surfaces
___ is the most common worm infection in the US
The hallmark symptom for infection with this bug is ___
Pinworm
Anal itching
Dx of pinworm infection
Rx of pinworm infection
Dx: Scotch tape test (bring piece of scotch tape on anal area, if worms present, they’ll stick there and you can visualize them on microscopy) or pinworm paddle
Rx: Combantrin (aka Pyrantel pamoate aka PAM from Sketchy): depolarizes muscles and causes paralysis of the worms
Hookworm (aka Ancylostoma duodenale or Necator americanus) life cycle
Larvae penetrate the skin >> enter blood >> traffic to lungs, migrate up respiratory tree to trachea >> swallowed >> to small intestine develop to adults
***
In feces, embryonated eggs hatch and become L1s. L1s feed on bacteria >> L2s >> migrate out of soil and become L3s >L3 = infective stage >> L3 become motile and wait to be picked up thru someone’s feet >> attach to feet and secret enzymes that allow them to burrow thru skin >> find blood vessel >> heart >> lungs >> alveolar space (L3 to L4 development) >> throat >> swallowed >> intestine >> adult male/female differentiation >> females lay eggs
*these bugs get their nutrition from popping capillaries and lymphatics and sucking blood out of them*
Hallmark symptom of hookworm infection is __
Rx for hookworm infection
Itching/rash at larvae penetration site
Rx: Albendazonle / Mebendazole (the bendy wires in the tunnel in sketchy)
MOA of Albendazole/Mebendazole
MOA of Albendazole/Mebendazole: disrupt microtubules + block parasite uptake of micronutrients (think microtubules are tubes that you’re bending and breaking)
Which bug causes the pathology below?
Hookworm (Ancylostoma duodenale or Necator americanus
Symptoms of chronic hookworm infection in kids vs adults
Lassitude
Weight loss
(Anemia + iron deficiency since they drink up blood)
In kids: + growth and mental deficits
Ascaris lifecycle
Lifecycle of Ascaris: females lay eggs that are released in the feces >> eggs contaminate the environment (eggs are long lived and resistant to environmental stresses)
Eggs are taken up in human host >> hatch in the intestine >> L21 larva burrow thru intestinal wall, migrate thru different places including lungs >> make their way back to intestine >> develop into males and females (females larger than males; live up to 2 years)
Rx for Ascaris infection
Albendazole/ Mebendazole
Piperazine Citrate – Blocks Ach signaling >> worm paralysis
Pyrantel pamoate
Ivermectine (Mectizan) - Blocks glutamate-gated chloride channels in nerve and muscle cells resulting in paralysis
**note that all these work to get the worm off the intestinal wall so it can get flushed out into the feces**
Whipworm lifecycle
Eggs taken up by human host >> hatch in small intestine >> move to colon (adults form here) >> attach to gut wall and drink blood
**this bug is similar to the hookworm in terms of drinking blood**
Lifecycle of Strongyloides (aka threadworm)
Lifecycle of Strongyloides: similar to hookworm life cycle except adults live in large intestine
**Also adults are only one sex
Auto-infection common with strongyloides infection; mainly affects immunocompromised folks**
Life cycle of trichinella spiralis
Cycles between rodents and pigs
Larvae in undercooked pork >>hatch in intestine >> break out and inhabit striated muscle tissue (muscle cells made to de-differentiate into nurse cells in which the larvae can survive for years)
2 manifestations of toxocariasis in humans are__(hint: eyes and skin)
Bugs can migrate to the eye >> ocular larva migrans (inflammation and scarring of the retina)
Bugs can also cause cutaneous infection >> cutaneous (visceral) larval migrans: tracks of larvae moving around leaves behind antigen that the immune system mounts an inflammatory response to
Lifecycle of Anisakis
Normal lifecycle in fish; transmission: eating sushi
Human ingests raw fish >> goes to intestine and replicates there >. Stays in intestine and causes bloody diarrhea, abdominal pain + distention
Rx: Surgery + Albendazole
Lifecycle of lymphatic filariasis bugs
How is this disease transmitted?
Transmission: mosquito bite
Female mosquito delivers L3 infective stage larva >> migrate to afferent lymphatics >> male and female reproduction >> eggs undergo ovoviviparous >> hatch inside female bug >> female releases fully formed larvae >> lymphatics >> thoracic duct >> left/right subclavian vein >> stays in circulation
**this part of the cycle happens in the human host. the stage in the mosquito is everything from L1 >>L3 (the mosquito takes a mature bug)
Lifecycle of O volvulus (causes onchocerciasis)
Similar life cycle to filariasis bugs except transmission is via the blackfly, and that the larvae don’t go to the lymphatics but go to other tissues
The adult cycle happens inside a nodule (probably part of host response) and the female releases fully formed L1 larvae into the periphery
The larvae leave the nodule and instead migrate underneath the skin
Examples of ocular pathology caused by O volvulvus are __ and __
Ocular pathology: punctate keratitis and sclerosing keratitis (causes river blindness)
2 manifestations of loa loa
Loa loa manifestations:
Calabar swelling – adult bugs are migratory and when they die, they cause inflammation and swelling
Bug can also crawl out of eye. (when removing bug, if the bug is squished too much it can pop and release antigens that cause a strong inflammatory response inside the eye >> may lead to loss of eye
